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Fuses, DIsconnects, and breakers on PV lines
Under the 2023 National Electrical Code (NEC), specific requirements exist for the installation and use of photovoltaic (PV) system components such as isolators, fuses, and circuit breakers. Here's a detailed explanation:
### PV Isolator (Disconnects)
A PV isolator, or disconnect switch, is used to safely isolate the PV system for maintenance, emergencies, or other purposes. Key points regarding PV isolators in the NEC 2023 include:
1. **Location Requirements (690.13)**:
- A disconnecting means must be installed for all PV system circuits.
- The disconnect must be located in a readily accessible location and clearly labeled.
- If the disconnect is outside the building, it should be within sight and within 10 feet of the PV system or clearly visible.
2. **Functionality (690.15)**:
- The isolator must be able to open all current-carrying conductors simultaneously.
- It must be rated for the voltage and current requirements of the PV system.
- Must have a visible break or indication of open status.
3. **Marking and Identification (690.14)**:
- Isolators must be permanently marked with their purpose.
- Appropriate signage must indicate the presence and function of the disconnect.
### Fuses
Fuses in PV systems protect against overcurrent conditions, preventing damage to the conductors and components. NEC 2023 stipulates:
1. **Overcurrent Protection (690.9)**:
- Each source circuit, output circuit, and battery circuit must have overcurrent protection.
- Fuses must be rated for the voltage and current expected in the circuit.
- They must be suitable for use in DC circuits if used on the DC side of the system.
2. **Location and Accessibility (690.16)**:
- Fuses must be placed in locations that are accessible for replacement.
- If located in combiners or similar enclosures, the enclosure must be listed for the application.
3. **Temperature Rating (690.8)**:
- Overcurrent protection devices must be rated for the highest temperature they will encounter in service.
### PV Circuit Breakers
Circuit breakers serve a similar overcurrent protection function as fuses but can be reset. NEC 2023 requirements include:
1. **Suitability for PV Systems (690.9)**:
- Circuit breakers must be listed and labeled for the application, including DC ratings if used on the DC side.
- Must have appropriate voltage and current ratings for the PV circuits they protect.
2. **Series and Parallel Applications (690.8)**:
- When used in series or parallel configurations, breakers must handle the combined voltage and current characteristics of the system.
3. **Accessibility and Maintenance (690.15)**:
- Circuit breakers should be installed in readily accessible locations for maintenance and reset.
### Specific Situations
1. **DC to DC Converters (690.71)**:
- Isolators, fuses, and breakers are also required for DC to DC converters, with similar requirements as for other PV system components.
2. **Rapid Shutdown (690.12)**:
- PV systems on buildings must have a rapid shutdown function for the array, which often involves isolators and disconnects to de-energize the system quickly.
Under the 2023 National Electrical Code (NEC), specific requirements exist for the installation and use of photovoltaic (PV) system components such as isolators, fuses, and circuit breakers. Here's a detailed explanation:
### PV Isolator (Disconnects)
A PV isolator, or disconnect switch, is used to safely isolate the PV system for maintenance, emergencies, or other purposes. Key points regarding PV isolators in the NEC 2023 include:
1. **Location Requirements (690.13)**:
- A disconnecting means must be installed for all PV system circuits.
- The disconnect must be located in a readily accessible location and clearly labeled.
- If the disconnect is outside the building, it should be within sight and within 10 feet of the PV system or clearly visible.
2. **Functionality (690.15)**:
- The isolator must be able to open all current-carrying conductors simultaneously.
- It must be rated for the voltage and current requirements of the PV system.
- Must have a visible break or indication of open status.
3. **Marking and Identification (690.14)**:
- Isolators must be permanently marked with their purpose.
- Appropriate signage must indicate the presence and function of the disconnect.
### Fuses
Fuses in PV systems protect against overcurrent conditions, preventing damage to the conductors and components. NEC 2023 stipulates:
1. **Overcurrent Protection (690.9)**:
- Each source circuit, output circuit, and battery circuit must have overcurrent protection.
- Fuses must be rated for the voltage and current expected in the circuit.
- They must be suitable for use in DC circuits if used on the DC side of the system.
2. **Location and Accessibility (690.16)**:
- Fuses must be placed in locations that are accessible for replacement.
- If located in combiners or similar enclosures, the enclosure must be listed for the application.
3. **Temperature Rating (690.8)**:
- Overcurrent protection devices must be rated for the highest temperature they will encounter in service.
### PV Circuit Breakers
Circuit breakers serve a similar overcurrent protection function as fuses but can be reset. NEC 2023 requirements include:
1. **Suitability for PV Systems (690.9)**:
- Circuit breakers must be listed and labeled for the application, including DC ratings if used on the DC side.
- Must have appropriate voltage and current ratings for the PV circuits they protect.
2. **Series and Parallel Applications (690.8)**:
- When used in series or parallel configurations, breakers must handle the combined voltage and current characteristics of the system.
3. **Accessibility and Maintenance (690.15)**:
- Circuit breakers should be installed in readily accessible locations for maintenance and reset.
### Specific Situations
1. **DC to DC Converters (690.71)**:
- Isolators, fuses, and breakers are also required for DC to DC converters, with similar requirements as for other PV system components.
2. **Rapid Shutdown (690.12)**:
- PV systems on buildings must have a rapid shutdown function for the array, which often involves isolators and disconnects to de-energize the system quickly.
